Scientific Forecaster Discussion

Area forecast discussion National Weather Service New York New York 315 PM EDT sun Aug 2 2015

Synopsis... high pressure tonight will give way to a slow moving cold front Monday and Monday night. The cold front moves east of the area on Tuesday...and then weak high pressure builds over the area on Wednesday. Several areas of low pressure may impact the area for the end of the week.

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Near term /until 6 am Monday morning/... upper level shortwave...jet dives from Canada toward the northern and western Great Lakes region tonight...amplifying the trough with resultant lowering of heights upstream.

As such...patchy fog is forecast for later tonight. As previous shift mentioned...some stratus is possible...but current thinking is fog development the more likely result.

Temperatures will fall into the 60s and 70s per MOS. Blend used.

There is a moderate risk for the development of rip currents at the ocean beaches this evening.

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Short term /6 am Monday morning through Monday night/... persistent trough/closed low will make slow progress east through this time frame. Surface cold front approaches from the west...making slow progress toward the area late Monday and Monday night.

A dry start to the day is forecast...with increasingly humid conditions.

Under a good deal of sunshine...and warm air advection ahead of the upper trough and surface frontal boundary...temperatures will warm well into the 80s...and will approach or exceed 90 away from the south coasts. Blended met/mav and ecs.

12z model suite continues to show slow movement to the front and upper level lift and thus slow progression and development of any showers/thunderstorms into our area. Much of the area remains dry through late afternoon. Better chance Monday night due to approaching middle level lift as it pivots around the trough...and as the surface frontal boundary moves across the region. NAM looks to be slightly slower with cold frontal progression east. Coverage of convection should remain scattered at best.

As for storm strength...if any storms make into our northwest zones late in the day...ample wind shear along with marginal to moderate instability could help sustain a few stronger storms. This is true into Monday night as well.

Another warm night is anticipated as clouds increase and S/SW deep flow persists.

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Long term /Tuesday through Sunday/... cold front moves east of the area during the day Tuesday. Meanwhile...a deep closed upper low over central Canada moves into eastern Canada. This will result in an upper trough that will linger over the northeast for the middle to the end of the new week. Generally cool and unsettled conds on tap for this period.

Showers taper off from west to east Tuesday morning as the cold front works its way across the region. Conds dry out from late morning through early afternoon...and then an upper shortwave will rotate around the base of the upper trough and through the northeast. This will touch off some scattered showers/thunderstorms across the region in the late afternoon. Since it will take some time for the cooler and less humid air to make its way into the local area...can expect highs in the upper 80s to around 90. Surface dewpoints will fall into the low 60s across western zones during the day...but dewpoints will remain in the upper 60s for eastern zones. As a result...the heat index will generally be around 90 throughout.

Surface high pressure then passes through the region on Wednesday. No precipitation expected...and a cooler and dryer airmass spreads into the region with highs generally in the 80s and dewpoints in the 50s. High pressure moves off the middle-Atlantic coast Wednesday night.

From Thursday through Sunday...with an upper trough over the northeast...several waves of low pressure will develop at the base of the trough and will pass through the mid-Atlantic/northeast during this time. Models have had a hard time picking up on the track of each low and have resulted in different tracks with each run...but it is still too far out in time to say what will happen. Will carry chance probability of precipitation during this time...as at least 2 different areas of low pressure will track through the region with conds drying out by Sunday.

Temperatures will run several degrees below normal during this time with highs in the upper 70s to low 80s.

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Aviation /19z Sunday through Friday/... high pressure builds into the region tonight.

S-SW winds less than 10 knots inland...and around or just over 10 knots along the coast. Late day south-southeast sea breeze are expected at kewr/kteb.

VFR at most terminals...with exception of kgon which should fluctuate between VFR and MVFR overnight on this first night of onshore flow.

Marine... southerly winds will continue tonight as high pressure passes east. A cold front approaches the waters Monday...moving close to the waters Monday night. Winds out ahead of the front increase Monday afternoon into Monday night before lightening with the approach of the front.

Ocean seas build due to the increase in these winds. After collab with surrounding offices...will issue Small Craft Advisory beginning 20z Monday afternoon and through Monday night.

Winds and seas will gradually subside below Small Craft Advisory levels on Tuesday...and then weak high pressure passes through the waters on Wednesday. For the end of the week...several areas of low pressure may pass across the waters...resulting in occasional Small Craft Advisory conds for at least the ocean waters.

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Hydrology... locally heavy rainfall is possible in thunderstorms late Monday/Monday night and again Tuesday afternoon/evening east of NYC...which could lead to minor poor drainage flooding.